US2618749A - Electrical impedance unit - Google Patents

Description

NOV 18, 1952 E. c. ALTENBr-:RGER

ELECTRICALMPEDANCE UNIT Filed Feb. 25, 1950 vlu,

L S ATTORNEYS ltvatentecl Nov. i8, 149522 ELECTRICAL IMPEDANCE UNIT Edmund C. Altenbergcr, Plainfield, N. J., assignor to Essex Electronics, a corporation of New Jersey Application February 25, 1950, Serial No. 146,267

4 Claims.

This invention relates to an adjustable capacitor and more particularly to an adjustable capacitor for varying the coupling inv a capacity coupled radio-frequency transformer unit.

Where capacitative coupling is employed between the primary and secondary of radio-frequency transformer units, which require the shield or can in which the transformer is enclosed, to be opened in order for the capacitor to be adjusted, properly to tune the circuit in which the transformer is used, such adjustment is time consuming 1in that it requires the can to be removed for each adjustment and in addition as the characteristics of the circuit will change when such can is removed, an adjustment made under such conditions may not be correct when the can is restored for normal operation.

Where conventional trimmer capacitors of the type using movable plates are employed for such capacitative coupling, in addition to the relatively high cost of such capacitors in relation to the cost of the other components used in the unit, the unit must be made of larger size in order to accommodate such capacitor and where many radio frequency transformers are used, as in a radio receiver, the overall increase in size of the receiver unit may be objectionable, especially when such receivers are used in small, compact devices such as guided missiles or the like.

It is accordingly among the objects of the invention to provide a capacitor that may be incorporated in a radio-frequency transformer unit without any material increase in the size or cost thereof and which may readily be adjusted properly to tune the circuit without opening the can in which the transformer is housed.

' prises a substantially tubular body of dielectric material with a conductive metallic outer surface as one electrode and a conductive metallic element, extending longitudinally with small clearance in the bore of the body and adjustable lengthwise thereof, as the other electrode. Preferably the metallic element in the bore of said tubular body is a wire protruding from one end of such bore, and the metallic outer surface of said tubular body is desirably a conductive coating, whereby when the length of wire in the bore of the tubular body is varied the value of the capacitance will be correspondingly changed.

In a specific embodiment herein shown to illustrate the invention, the tubular body is desirably mounted on the base of a radio-frequency transformer, preferably extending laterally of the coil form of said transformer, with the end of the wire which extends from said tubular body being aflixed to one of the terminal lugs of the unit.

In the accompanying drawings in which is shown one of various possible embodiments of the several features of the invention,

Fig. l is a perspective view of a radio frequency transformer incorporating the present invention,

Fig. 2 is a longitudinal sectional view taken along line 2-2 of Fig. l,

Fig. 3 is a transverse sectional view taken along line 3-3 of Fig. 2, and

Fig. 4 is a view similar to Fig. 3 of another embodiment of the invention.

Referring now to the drawings, a metal can or shield I0 is affixed at its rim in conventional manner about a base I I of insulating material, such as Bakelite upon which the radio frequency transformer unit is mounted. The base illustratively has four terminal lugs I2, one at each corner thereof and desirably protruding beyond the under and upper face thereof. An upstanding coil form I3 is mounted on the base II and illustratively has two coils I4 and I5 wound thereon.

The transformer is desirably resistance loaded in the illustrative embodiment shown herein, by means of a pair of resistors I6 and I1, the terminals I8 and i9 of each of which are affixed to the upper protruding ends of the pair of terminal lugs I2 to which the ends of coils I4 and I5 respectively are also affixed.

To provide for capacitative coupling between coils I 4 and I5 a capacitor unit 2| is provided which is adjustable in order that the circuit in which the transformer is used may be tuned.

According to the invention the capacitor unit 2I as shown in the drawings desirably comprises a tube 22 of dielectric material such as ceramic, having a metallic element or electrode 23 on the outer surface thereof desirably a coating of conductive metallic paint as shown in Figs. 1 to 3. or, if desired, instead of a coating of metallic paint, a metal sleeve 23 could be used as shown in Fig. 4. Tube 22 is preferably a'ixed in a vertical bore 24 in base II so as to be securely retained therein with the lower end of the tube desirably substantially flush with the under surface of the base I I and with the upper portion of the tube extending above the surface of base II laterally of coil form I3.

A metallic element or electrode, desirably a wire 25, is positioned in the bore of said tube 22 so as to be adjustable lengthwise thereof. The diameter of said bore is desirably only slightly greater than the diameter of said wire so as to provide but slight clearance therebetween and one end of said wire extends from the lower end of said bore. The outer extremity of said wire is affixed as by soldering as at 26 to one of the terminal lugs I2, illustratively the terminal lug to which one of the ends of coil I5 is axed. Preferably the portion of Wire 25 extending from tube 22 is reversely bent as at 21 to provide sufcient length of wire to permit movement thereof into the bore of said tube.

In order to complete the circuit, the metallic element 23 or 23 on the outer surface of tube '22, preferably at the upper end thereof, has a lead 28 aixed thereto as by soldering, with the free end 29 of said lead connected to one of the terminal lugs I2 to which one of the ends of coil I4 is also affixed.

After the assembled transformer unit is installed in conventional manner on the chassis of a radio receiver or other device in which it is to be used, it may readily and quickly be tuned from the under side of the chassis without removal of the can I0, by moving the lead 25 with respect to the bore of the tube 22 so that more or less of the lead is within such bore. Thus the elfective capacitance of the condenser unit 2I will be varied to tune the circuit and a drop of cement 32 may be placed on the lower end of the tube securely to retain the lead in its fixed selected position therein when the transformer is properly tuned.

It is to be noted that if the can I9 must be removed for the tuning operation, as the characteristics of the circuit would be diiferent when the can was restored, although the circuit may be tuned with the can removed when such can is replaced the circuit might again be out of tune. This difficulty is avoided by the arrangement and construction of the unit herein described.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limitingr sense.

Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

1. A radio frequency transformer comprising a base, a coil form mounted on said base, a pair of coils wound about said form, a tubular body of dielectric material mounted on said base extending laterally of said coil form with the upper portion of said tubular body extending above the upper face of said base, said tubular body having an electrode on the outer surface thereof, a lead connecting said electrode to one of said coils,

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and a wire extending longitudinally in the bore of said tubular body and protruding from the lower end thereof on the under surface of said base and axed to a lead from the other of said coils, the diameter of said bore being only slightly greater than the diameter of said wire to provide but slight clearance therebetween thereby to afford sliding movement of said wire in said bore.

2. The combination set forth in claim. 1 in which the portion of said wire protruding from the end of said tubular body is of length to permit movement of said wire into said bore.

3. The combination set forth in claim 1 in which said tubular body extends laterally of said coil form.

4. A radio frequency transformer comprising a base of insulating material, at least four contact lugs on said base, an upstanding coil form alxed at one end to said base, a pair of coils wound about said form, the terminals of one of said coils being connected to one pair of lugs respectively and the terminals of the other of said coils being connected to the other pair of lugs respectively, a tubular body of dielectric material mounted on said base extending laterally of said coil form with the upper portion of said tubular body extending above the upper surface of said base, said tubular body having an electrode on the outer surface thereof, a lead connecting said metallic electrode to one of the lugs to which a terminal of one of said coils is affixed, a wire extending longitudinally in the bore of said tubular body and protruding from the lower end thereof on the under surface of said base and affixed to the depending end of one of the lugs to which a terminal of the other of said coils is connected, the diameter of said bore being only slightly greater than the diameter of said wire to provide but slight clearance therebetween thereby to afford sliding movement of said wire in said bore.

EDMUND C. ALTENBERGER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS

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